Subject: Benefit from amplification of high frequencies in hearing impaire From: Martin Vestergaard <MVE(at)OTICON.DK> Date: Thu, 22 Jul 2004 22:44:13 +0200Dear all, [Sorry for any duplication] I'm pleased to announce the availability of the following PhD thesis: Benefit from amplification of high frequencies in hearing impaired: aspects of cochlear dead regions and auditory acclimatization I you want a copy, - for a pdf version, browse to www.at.oersted.dtu.dk/~mve/archives/ - for a printed copy, send me an email with your address There's an abstract below! Cheers, MArtin ps: if you've already asked me for a printed copy and you haven't received it yet, please send me an email with your current address ____________________________ Martin D. Vestergaard, PhD Research Centre Eriksholm Kongevejen 243 DK-3070 Snekkersten Tel: +45 4829 8912 Abstract The thesis deals with the benefit that hearing-impaired people receive from amplification of high frequencies. Sounds brought back to audibility by hearing aids are expected to provide usefulness for users of hearing aids in terms of better auditory function, in particular better speech identification ability. While the rationales underlying provision of amplification to hearing-impaired patients are well-known, sometimes it happens that audibility does not provide the expected benefit for the patient. In the thesis, two theories are suggested for explaining why audibility may fail to provide functional benefit to the users of hearing aids: (1) cochlear dead regions and (2) auditory acclimatization. Two studies have been carried out to assess the feasibility of the two concepts. A study on cochlear dead-regions investigated the viability of a recent tool for diagnosing dead regions and looked at the possible implications of dead-region candidacy for speech-recognition ability in hearing-aid users accustomed to high-frequency amplification. A second study on auditory acclimatization in first-time hearing-aid users focused on longitudinal effects in objective and subjective hearing-aid outcome for patients with precipitous hearing loss. The results show that the two theories to some extent can explain failure to benefit from audibility. Patients with cochlear dead regions may not receive increased benefit from increased audibility to the same extent as patients without dead regions. However, dead-region patients show a more efficient use of audibility leaving the reduced benefit from increased audibility less salient in practice. Patients fitted with hearing aids that provide a substantial amount of audibility, are able to improve auditory performance over time. The strongest effect is seen in patients who initially do not perform as well as expected. However, some severely impaired patients had developed a better-than-expected ability to interpret low-frequency speech cues. Age, severity of the hearing loss and cognitive skills can predict to some extent if a patient is likely to improve auditory performance over time. In the subjective-benefit domain, it is observed that outcome dimensions addressed in various scales are not operational for hearing-aid users right from the time of initial fitting. It can take up to 3 months before a meaningful outcome space has been formed, and during that time, the relative importance of different outcome scales changes. The clinical ramification of the results from the two studies is threefold. First, initial objective hearing-aid benefit may not reflect the level of auditory performance that can be achieved after acclimatization to the amplification. Second, early subjective outcome-assessment may not reflect the true subjective benefit that the hearing-aid users experience. Third, possible dead regions in the cochlea of patients may blur the situation in that severely impaired patients may perform better than expected initially.